Interline charge-coupled devices

Abstract

Image capturing systems with interline CCD structures designed to reduce the delay between captures of subsequent image frames are disclosed. Proposed interline CCD structures include two or more sets of storage units associated with a given set of photodetecting elements, where each photodetecting element is associated with one storage unit of each set of storage units in that the charge generated by the photodetecting element during the acquisition of a particular image frame (i.e. during a particular exposure period) may be stored any one of these storage units prior to read-out. Providing multiple sets of storage units allows read-out of charge corresponding to one image frame and stored in one set of storage units while accumulating charge corresponding to another image frame in another set of storage units, thus reducing the delay between captures of different image frames. Consequently, errors and artifacts of the image capturing system can be minimized.

What is claimed is: 
     
       1. An image acquisition system comprising:
 an interline charge-coupled device (CCD) sensor comprising
 a plurality of photodetecting (PD) elements, 
 a plurality of first CCD storage units for storing a charge accumulated by the plurality of PD elements during an acquisition of one image frame comprising multiple exposures, and 
 a plurality of second CCD storage units for storing a charge accumulated by the plurality of PD elements during an acquisition of another image frame comprising multiple exposures, 
 wherein the charge accumulated by the plurality of PD elements during the acquisition of the one image frame and of the another image frame is transferred from the plurality of PD elements by keeping a transfer gate for each of the plurality of PD elements open during the acquisition of the one image frame and of the another image frame and varying a substrate voltage to drain a portion of the charge accumulated by the plurality of PD elements in between the multiple exposures of each of the one image frame and the another image frame out of the plurality of PD elements; and 
 
 a controller for controlling that at least a part of the charge accumulated during the acquisition of the one image frame is read out during the acquisition of the another image frame. 
 
     
     
       2. The image acquisition system according to  claim 1 , wherein each PD element of the plurality of PD elements is associated with a first CCD storage unit of the plurality of first CCD storage units and with a second CCD storage unit of the plurality of second CCD storage units. 
     
     
       3. The image acquisition system according to  claim 2 , wherein the first CCD storage unit associated with the PD element is provided on the same lateral side of the PD element as the second CCD storage unit associated with the PD element. 
     
     
       4. The image acquisition system according to  claim 2 , wherein the first CCD storage unit associated with the PD element is provided on a different lateral side of the PD element as the second CCD storage unit associated with the PD element. 
     
     
       5. The image acquisition system according to  claim 3 , wherein said one image frame is a second image frame and said another image frame is a first image frame, and the controller is configured to control that:
 the plurality of PD elements transfer the charge accumulated by the plurality of PD elements during the acquisition of the first image frame to the plurality of first CCD storage units, and 
 the plurality of first CCD storage units transfer the charge accumulated during the acquisition of the first image frame and obtained from the plurality of PD elements to the plurality of second CCD storage units. 
 
     
     
       6. The image acquisition system according to  claim 5 , wherein the controller is further configured to control that, following the transfer from the plurality of the first CCD storage units to the plurality of second CCD storage units, the plurality of PD elements transfer the charge accumulated by the plurality of PD elements during the acquisition of the second image frame to the plurality of first CCD storage units. 
     
     
       7. The image acquisition system according to  claim 4 , wherein said one image frame is a first image frame and said another image frame is a second image frame, and the controller is configured to control that:
 the plurality of PD elements transfer the charge accumulated by the plurality of PD elements during the acquisition of the first image frame to the plurality of first CCD storage units, and 
 the plurality of PD elements transfer the charge accumulated by the plurality of PD elements during the acquisition of the second image frame to the plurality of second CCD storage units. 
 
     
     
       8. The image acquisition system according to  claim 4 , wherein the plurality of first CCD storage units comprises a vertical CCD while the plurality of second CCD storage units comprises a horizontal CCD or vice versa. 
     
     
       9. The image acquisition system according to  claim 1 , wherein each of the plurality of first CCD storage units and the plurality of second CCD storage units comprises a vertical CCD or each of the plurality of first CCD storage units and the plurality of second CCD storage units comprises a horizontal CCD. 
     
     
       10. The image acquisition system according to  claim 1 , further comprising an illumination source configured to provide light detected by the plurality of PD elements. 
     
     
       11. The image acquisition system according to  claim 10 , wherein the light provided by the illumination source comprises pulsed light. 
     
     
       12. The image acquisition system according to  claim 11 , wherein the image acquisition system is a Time-Of-Flight system, further comprising one or more processors configured to determine distance to one or more objects based on the acquired image frames. 
     
     
       13. A non-transitory computer readable storage medium storing software code portions configured for, when executed on a processor, carrying out a method for controlling an interline charge-coupled device (CCD) sensor comprising a plurality of photodetecting (PD) elements, a plurality of first CCD storage units for storing a charge accumulated by the plurality of PD elements during an acquisition of one image frame, and a plurality of second CCD storage units for storing a charge accumulated by the plurality of PD elements during an acquisition of another image frame, the method comprising
 reading out at least a part of the charge accumulated during the acquisition of the one image frame comprising multiple exposures during the acquisition of the another image frame comprising multiple exposures, 
 wherein the charge accumulated by the plurality of PD elements during the acquisition of the one image frame and of the another image frame is transferred from the plurality of PD elements by keeping a transfer gate for each of the plurality of PD elements open during the acquisition of the one image frame and of the another image frame and varying a substrate voltage to drain a portion of the charge accumulated by the plurality of PD elements in between the multiple exposures of each of the one image frame and the another image frame out of the plurality of PD elements. 
 
     
     
       14. The non-transitory computer readable storage medium according to  claim 13 , wherein said one image frame is a second image frame and said another image frame is a first image frame, and the method further comprises:
 transferring the charge accumulated by the plurality of PD elements during the acquisition of the first image frame to the plurality of first CCD storage units, 
 transferring the charge accumulated during the acquisition of the first image frame from the plurality of first CCD units to the plurality of second CCD storage units, and 
 following the transfer from the plurality of the first CCD storage units to the plurality of second CCD storage units, transferring the charge accumulated by the plurality of PD elements during the acquisition of the second image frame to the plurality of first CCD storage units. 
 
     
     
       15. The non-transitory computer readable storage medium according to  claim 13 , wherein said one image frame is a second image frame and said another image frame is a first image frame, and the method further comprises:
 transferring the charge accumulated by the plurality of PD elements during the acquisition of the first image frame to the plurality of first CCD storage units, and 
 transferring the charge accumulated by the plurality of PD elements during the acquisition of the second image frame to the plurality of second CCD storage units. 
 
     
     
       16. The non-transitory computer readable storage medium according to  claim 13 , wherein the method further comprises performing Time-Of-Flight computations to determine distance to one or more objects based on the acquired image frames. 
     
     
       17. An interline charge-coupled device (CCD) image acquisition system comprising:
 a plurality of photodetecting (PD) elements, 
 two sets of CCD storage units, each set of CCD storage units for storing a charge accumulated by the plurality of PD elements during an acquisition of a respective image frame comprising multiple exposures, and 
 a controller for reading out at least a part of the charge stored in one set of CCD storage units during the acquisition of an image frame the charge for which is accumulated in another set of CCD storage units, 
 wherein the charge accumulated by the plurality of PD elements during the acquisition of the respective image frame is transferred from the plurality of PD elements by keeping a transfer gate for each of the plurality of PD elements open during the acquisition of the respective image frame and varying a substrate voltage to drain a portion of the charge accumulated by the plurality of PD elements in between the multiple exposures of the respective image frame out of the plurality of PD elements. 
 
     
     
       18. The interline CCD image acquisition system according to  claim 17 , wherein each PD element of the plurality of PD elements is associated with one CCD storage unit of the plurality of first CCD storage units and with one CCD storage unit of the plurality of second CCD storage units.